In current communication networks designed according to the asynchronous transfer mode (ATM), in particular subscriber terminal networks and feeder networks (ACCESS networks, e.g. passive optical networks or fiber coax networks), the available network resources are partitioned to network terminal units connected to the communication network, or are partitioned to the communication terminal apparatuses connected to the network terminal units. The access of the network terminal units or communication terminal devices to the transmission medium used in common (e.g. light waveguides or radio channels) is controlled by an algorithm that is normally realized by hardware, given a high transmission speed and a plurality of connected communication terminal devices, the algorithm granting access authorization to a network terminal unit requesting communication network resources.
In already-installed subscriber terminal networks, for each network terminal unit a timer or counter is realized, for example in a network control unit connected with each network terminal unit, the timer being started in the context of connection setups introduced by the network terminal units. A timer runs out or the counter reaches a predetermined value, as soon as a new data packet is filled with useful data in a relevant network terminal unit and is intermediately stored for data transmission in a buffer memory likewise realized in the network terminal unit. The dimensioning of the counter or the time until the running out of a timer occurs dependent on the data transmission rates respectively reserved during the connection setups. A signaling signal that indicates the running out of a timer represents a request for a transmission authorization on the transmission medium used in common. The request is individual to the network terminal unit and is stored sequentially in a memory (e.g., a FIFO memory) that is realized in the network control unit and is used in common by all the network terminal units. The stored transmission authorizations are read out from this memory and are transmitted, as the actual transmission authorization, to the network terminal units or communication terminal apparatuses, which thus receive access to the transmission medium. Two timers can, for example, run out at the same time, i.e. two isochronous access authorizations would have to be stored and controlled. Since, however, two isochronous accesses are not possible, one of the two access authorizations is delayed until the current access is terminated. This delaying is designated xe2x80x9ccell delay variation.xe2x80x9d Given running out of several timers at the same time, the value of the cell delay variation is correspondingly increased.
In addition, it has already been proposed that the transmission authorizations requested by the network terminal units be acquired and stored directly by means of a central control unit, and that the requested transmission authorizations be uniformly distributed on the transmission medium used in common.
The methods described above for the assigning of transmission authorizations can be realized only for a limited number of network terminal units or communication terminal apparatuses. In addition, the delay times in which the network terminal units receive the access to the transmission medium comprise statistical fluctuations or a differing cell delay variation. The value of the cell delay variation depends on the data transmission rates of all connections set up, and becomes very large when the overall data transmission rate of the transmission medium used in common approximates the value 100%. The large delay times cause an overflow of buffer memories, and thus an extreme increase in the error rate in the data transmission, which results in a break off of set-up connections, In accordance with protocol.
It is an object of the invention to optimize the use of predetermined switching-oriented and transmission-oriented resources in a packet-oriented communication network.
According to the apparatus and method of the present invention, accesses of network terminal units to predetermined resources of a packet-oriented communication network are controlled. Annularly chained memories are allocated to the network terminal units, the chained memories being sampled cyclically and which represent predetermined partial communication network resources. In the context of connection setups introduced by the network terminal units. requested partial communication network resources are assigned to the network terminal units by entering access authorizations into the annularly chained memories. Given a sampling of an annularly chained memory, access is currently granted to the assigned partial communication network resources corresponding to the entered access authorization of the relevant network terminal unit.
An important aspect of the method of the invention for controlling accesses of network terminal units to predetermined resources of a packet-oriented communication network is in the allocation of annularly chained memories to the network terminal units, whereby the successive memories, which can be sampled cyclically, represent predetermined partial communication network resources. In the context of connection setups introduced by the network terminal units, requested partial communication network resources are allocated to the network terminal units by entering access authorizations into the annularly chained memories. When an annularly chained memory is sampled, access is currently granted to the allocated partial communication network resources, corresponding to the entered access authorization of the relevant network terminal unit.
The essential advantage of the method of the invention is that the predetermined resources of a packet-oriented communication network can be arbitrarily distributed to many network terminal units arranged therein, whereby the packet-oriented communication networks, e.g. packet networks such as ATM networks, however also comprise local packet-oriented communication networks (e.g., bus networks, ring networks or star networks). In addition, these predetermined resources (e.g., a transmission rate of 622 Mbit/s or 2.6 Gbit/s) can be assigned to a single network terminal unit as needed.
Advantageously, given a signaling from the network terminal units that modifies the scope of the requested partial communication network resources, or given a signaling from the packet-oriented communication network that indicates a modification of the availability of the predetermined resources, the allocation of the requested partial communication resources is carried out again. By means of this advantageous construction, current changes in the requested partial communication network resources are taken into account, so that the available predetermined resources of the packet-oriented communication network are distributed optimally to the network terminal units respectively currently containing or switching a connection.
According to a further advantageous construction, further annularly chained memories, constructed corresponding to the annularly chained memories, are allocated to the network terminal units, whereby the access authorizations are entered for the first time into the annularly chained memories or further annularly chained memories, and the controlling of accesses of network terminal units is currently controlled by these memories. Upon each change of access authorizations, all access authorizations are determined anew, and are entered into the memory not currently being used for controlling accesses. After this entering, after the current granting of an access these memories are used for controlling accesses. By means of this advantageous construction, an entering of access authorizations into the annularly chained memories is possible during running operation. Thus, during the sampling of the annularly chained memories a new allocation of access authorizations to the annularly chained memories (e.g., initiated by a connection setup of a network terminal unit) is determined in the background, i.e. in parallel, and subsequently the determined access authorizations are entered, during operation, into the chained memories respectively not currently used for controlling accesses. In this way, a rapid and effective controlling of access authorizations can be realized.
Advantageously, in the context of the connection setup the delay of the accesses of the network terminal units to the allocated partial communication network resources is determined by the occupation of the annularly chained memories. During access to the allocated partial communication network resources, the determined delays are not exceeded. By means of this advantageous construction, the delay of the accesses of the network terminal units to the transmission medium used in common (cell delay variation) is known already during the connection setup phase, and is guaranteed even given a full-capacity utilization of the predetermined resources of the packet-oriented communication network for each connected network terminal unit, i.e., the determined delays are thus maximum delays of the packets to be transmitted, which are not exceeded.
According to a further advantageous construction, the access authorizations of the network terminal units are entered into the annularly chained memories in such a way that the accesses to the allocated partial communication network resources are optimized according to predetermined criteria. Such a predetermined criterion presents for example the minimum delay of the accesses of the network terminal units to the allocated partial communication network resources. By means of this advantageous constructive feature, connections can be realized with a minimum delay of the accesses of the corresponding network terminal units, i.e. with a minimum cell delay variation, which are suitable in particular for the transmission of time-critical data (e.g., speech or video data), whereby the optimized delays are not exceeded.
The packet-oriented communication network is advantageously realized by means of a communication network designed according to the asynchronous transfer mode (ATM), and the predetermined resources of the packet-oriented communication network are advantageously represented by the transmission capacity of the wire-bound, optical, or wireless transmission paths in the feeder network of the packet-oriented communication network. Such wire-bound, optical or wireless transmission paths are, for example, realized between a network control unit that carries out the method of the invention and the packet-oriented communication network, or between the network control unit and the network terminal units connected thereto (also designated subscriber terminal network).
Further advantageous constructions of the method of the invention, as well as a network control unit for controlling accesses to predetermined resources of a packet-oriented communication network, are also provided.
In the following, the method of the invention for controlling accesses of network terminal units to predetermined resources of a packet-oriented communication network are explained in more detail on the basis of two block switching diagrams.